JSFiddle - React, Tailwind, and code Playground

HTML

<input id="input" type="text" onkeyup="myVal(this, 'input')">

JavaScript

function myVal(test, test1) {
  var elem = document.getElementById(test1);
  if(elem.value.length == 8 || elem.value.length == 13 || elem.value.length == 18){elem.value = test.value+'-'}
}